The progressive farmer. [volume] (Winston, N.C.) 1886-1904, 1887-06-30
FORESTS AND RAINFALL.

The tangle Of decayed vegetation
which covers the ground beneath the
forests is of considerable thickness.
On top it consists altogether of the
decayed trunks, branches and leaves,
but it shades down into ordinary dark
colored soil at the depth of a few feet
from the surface. This, the decay
zone of the forest, lies between the
boughs of the air and the branches of
the roots. In it 60 on the most i'm
portant actions which take place in
forests-actions which affect the his
tory of land and sea. We shall there
fore have to consider it in a somewhat
painstaking way. The most evident
effect of this sheet of decaying wood,
and moss which feeds on the decay, is
on the rainfall of the region which it
mantles. When, after a season of
drought, a copious rain falls upon this
spongy mass, the water is for a long
time absorbed in the interstices and
does not flow to the river. Even in
times of very heavy rain the water is
slowly yielded to the streams after a
dry period Of many weeks this sponge
retains a good share of water. Alike
amount of rain falling on titled fields
or prairies slips quickly away to the
rivers, and thence to the sea The first
result is, that when the land is destitute
of forests it sheds water like house
roofs, breeding floods after every con
siderable rain, while in the forests the
rain is only slowly yielded to the
streams.
A second and less evident result of
the spongy character of the forest-bed
is that, by hindering the escape of the
rain-water to the rivers, it increases
the actual rainfall of the country. To
see the nature and Importance of this
action, we must turn aside for a mo
ment to consider the origin of the rain
when it falls upon the land. The original
source of this water-supply is the sea,
which sends into the lands a tolerably
regular annual store Of moisture.
When this falls as rain or snow, either
of two things happens-the water may
60 away directly to the sea, or it may
return to the atmosphere as vapor to
be again precipitated rs rain. The
chance of it's Incorporation is leterm-
ined by the speed with which it flows
to the streams. From a treeless region
it rapidly escapes in an extensive
district of virgin forest it may again
and again pass from earth to air, and
from air to earth.
The columns Of vapor, which in
times of summer rain may be seen
ascending from every great wood,
afford visible evidence of the effect of
forests on rainfall. They also may
show the observer some of the most
beautiful phenomena of atmospheric
circulation. In a summer rain-shower
the air above the trees becomes much
cooler than it is in the recesses below
their tents of foliage. This heated air
within the wood seeks to rise, and
escapes in great columns whenever
there is a wide gap between the
branches AS soon as it attains the
cooler level above, the moisture is
condensed, and the air, before trans
parent, becomes charged with steam.
To replace this ascending air, a broad
current drifts toward the emerging
streams of vapor, commonly from the
higher parts of the forest, where the
air, owing to the elevation Of the site,
is cooler than in the lower levels.
This repeated passage Of the mois-
ture from earth to cloud, and from
cloud to earth, greatly increases the
amount of force which the rain applies
in the falling drops to the earth's sur
face but the rank vegetation protects
the surface from the erosion which it
would otherwise bring about. Even
the forest-clad hillsides Of the Cumber-
land mountains, where the soil lies on
declivities Of great steepness, suffer
little wear as long as their natural pro-
lection is left to them. But as soon
as they are stripped of the garment of
wood which has been upon the region
ever since, in the far-off ages, they
came from the depths of the sea, they
wear with great rapidity. The erosion
is limited as long as they are forest
clad to the stream beds, and there is
hindered by the innumerable obstacles
| of the fallen trees and entangled drift
wood. The brooks which are strong
enough to clear their beds and cut into
the earth and rock, are few in number;